Device for coating a traveling sheet



Nov. 25, 1958 L. HoRNBosTr-:L

DEVICE FOR coATING A TRAVELING SHEET Filed Aug. 1e, 1955 -nid StatesPater;

, 2,861,541 p DEVICE Fon coATrNG A TRAVELING snaar Lloyd Hornbostel,Beloit, Wis., assignor to Beloit Iron Works, Beloit, Wis., a corporationof Wisconsin Application August 16, 1955, Serial N o. 528,698

6 Claims. (Cl. 118-119) This invention relates to the coating of atraveling sheet, and more particularly, to a device for applying coat-1ng to a traveling sheet.

Although the instant invention may be employed in a number of differentarts wherein a coating or film of material is applied to a travelingsheet (whether or not the film is to be permanently retained on thesheet), the instant invention may be employed to particular advantage inapplying a coating to a traveling paper webl and the invention will bedescribed primarily with respect to this use in the instant disclosure.As those skilled in the art well know, the application of coatings inliquid form to a traveling paper web provides a number of problems. Nodevices are known which are apparently adequate to `apply a trulyuniform coating initially on the web; and the usual procedure calls forthe use of a first means to apply coating material on the web and asecond means to :smooth out the material and give the coating someuniformity. This arrangement also leaves something to be desired in thatthe traveling sheet or web is quite flexible and only a limited amountof tension can be maintained thereon. The forces which may be used tourge a wiping device or doctor against the traveling web are thuslimited to the tension which the web will stand and these forces arerelatively small so that it is often difficult to apply a coatinguniformly to the web. Any slight irregularities in web thickness willtend to cause diculty. Even substantial irregularities in the amount ofcoating initially applied can cause diiculty in such an arrangement.

The instant invention is based upon a discovery that a number of thesedifficulties can be overcome by forming a nip between a first member anddoctor means to receive the coated sheet therethrough and resilientlyurging the first member against the doctor means to obtain the desiredpressure load at the nip. Preferably also the iirst member is itselflexible or yieldable and is actuated by fluid actuated means so that asubstantially uniform pressure will be applied across the full width ofthe sheet notwithstanding possible irregularities in sheet thickness,etc. which might cause low pressure differences if the first member werenot flexible.

It is, therefore, an important object of the instant invention to.provide an improved device for coating a traveling sheet.

It is another important object of the instant invention to provide animproved device for coating a traveling sheet comprising coating meanson one side of the sheet applying coating thereto, doctor means on thesame side Vof the sheet behind said coating means in the travel of saidsheet wiping `excess coating from the sheet, and shoe means on theopposite side of the sheet resiiiently urging said sheet against saiddoctor means to control the extent to which excess coating is wiped fromthe sheet.

Other and further objects, features and advantages of the presentinvention will become apparent to those skilled Yin the art from thefollowing detailed disclosure thereof and the drawings attached heretoand made a part hereof.

In the drawing:

The drawing shows a'sectional elevational view of a device embodyingthev instant invention.

As shown in the drawing:

The device 10 of the instant invention may be described generally ascomprising first means 11 on one side of the sheet W applying coatingthereto, second means 12 on the same side of the sheet W behind saidfirst means 11 in the travel of the sheet W urged against the sheet W towipe excess coating therefrom, third means 13 defining with said secondmeans a nip N-l receiving the coated sheet W, and fourth means 14resiliently urging the third means i3 against the second means 12tocontrol the pressure at the nip N-1 and the amount of excess ycoatingtom 16, end walls 17 and 18 and side walls such as the side wall 19, allupstanding Vfrom the bottom 16. Also, the tank 13 has false bottom walls20l and 21 slanting downwardly from the end walls 17 and 18 to providefa generally V-shaped cross-section to the bottom of the tank 15 and thetank 15 maintains a -level L of coating bath B therein. The coatingmeans or applicator roll 11 is partially submerged in the coating bath Band mounted on suitable bearings in the side walls (only one of which,19, is here shown). The applicator roll 11 is provided with the usualbearings and drive means (not shown) to afford rotation thereof inthedirection indicated by the arrow which is the same direction as thedirection of travel of the sheet W. The applicator roll 11 itself may beused to drive the sheet W in its direction of travel, or additionaldrive means such as pinch rolls 22 and 23 may drive the sheet at asecond nip N-Z, as indicated. The driven sheet W receives coating Yfromthe surface of the applicator roll 11 in the usual manner, but thecoating thus applied is not applied with the extent of uniformitydesired. Actually, an excess of coating material is applied by the'applicator roll 11. The thus coated sheet or web W moves forwardly inthe direction indicated by the arrows over the second means or doctorroll 12. The doctor roll 12 is mounted on bearings (not shown) o-n aframemember 24 suitably secured to the end wall 18 of the tank 15"as bya bolt and nut assembly 25. The frame 24 has an arm portion 24aextending upwardly to close running relation to the doctor roll 12 tominimize loss of coating material thrown from the rotating doctor roll12. To carry out this function the arm portion 24a, of course, extendsthe full length of the roll 12. Centrally mounted arm portions 24h inthe frame 24 (mounted on opposite sides of the frame) carry bearings anddrive means (not shown) for the doctor roll 12 so that the doctor roll12 may be rotated preferably in the direction opposite to the directionof web travel so as to accomplish the desired wiping effect mostsatisfactorily. A third arm member 24C extends upwardly along theuprunning side of the doctor roll 12 and presents a flexible wipingmember 26 which is received in a groove 24d in the arm 24e extending thefull length of the doctor roll 12 or the full width of the tank 15 andthe flexible wiping member ..6 is urged against the uprunning side ofthe doctor roll 12 by an expandible fluid pressure actuated tube 27(suitably connected to a source of air under pressure, not shown), so asto continuously wipe the uprunning side of the doctor roll clean justbefore it comes in contact with the bottom or coated side of the web W.

The mounting means for the shoe 13 or third means 13 hereinbeforementioned are carried on the side walls of the tank 15 and only themounting means on the side wall 19 will be described herein, because themounting '31 extending therefrom and connected thereto by a pivot pin 32for swingable movement about the shoulder 30.

lA stopmember 30a extends from the should 30 forwardly and presents astop surface 3017 which limits downward vswinging movement of the arm31. A iluid pressure actuated piston and cylinder assembly 33 (ofstandard construction) is connected to an upper portion of the shoulder30 by a pivot pin 34 and `to an intermediate portion of the arm 31 by apivot pin 3S and the power cylinder 33 is used to effect limitedswinging movement of theV arm 31 upwardly from the stop surface 30h. Theouter extremity of the arm 31 carries a rigid dishshaped member 36 whichforms the anchored or ilxed part of the fourthmeans 14 or diaphragmmeans 14 hereinbefore mentioned. The bowed or dish-shaped member 36extends the full width of the tank 15 or the full width of the travelingweb W and is rigidly secured to the arm 31, as by bolts 37, 37. Ailexible rubber diaphragm member 38 of substantially the same area as'the rigid member 36 is sealed to the peripheral portions of the rigidmember 36, as by bolt and nut'assemblies 39, 39, so as to form anair-tight chamber C between the vflexible member 38 and the rigid member36.

Fluid under pressure such as compressed air is supplied to the chamber Cthrough the line 40 and may be,

The shoe 13 is secured to the downward or bottom side of the exiblemember 38 and moves therewith. The shoe 13 is preferably made of aflexible material, such as partially vulcanized rubber, so that it maybend at least to a limited extent at various places along its length,the length of the shoe 13 being the full width of the tank 15 or thewidth of the web W. The shoe 13 may be made of other materials havinglimitedilexibility (since a great deal of bending or sharp bends thereofare not required) and preferably the shoe 13 is provided with a smoothfrictionless surface 13a at the nip defining portion thereof. The shoe13 is held against rotation and is flexibly yieldable to the diaphragmmeans 14 along the length of the shoe 13.

A cross-bar 41 extends the full length of the shoe 13 and is received inan oversize passageway 13b therein. The cross-bar 41 is suitably securedrigidly to the arm 31, as by a screw mounted support 42, so that thecrossy bar 41 limits vertical movement of the shoe 13. The purpose ofthe cross-bar is to prevent unnecessarily great downward movement of theshoe 13 when the arm 31 has been lifted out of nip-engaging relationshipand only the flexible diaphragm member 33 would ordinarily be lsupporting the shoe 13. On the other hand, the oversize passageway 13bpermits the desired limited bending or tlexible movement of the shoe 13when such is necessary.

As will be appreciated the arms 31, 31 are mounted n opposite sides ofthe tank 15 in the manner here described so as to support therebetweenthe diaphragm means 14 carrying the shoe 13.

It will be understood that modifications and variations may be effectedwithout departing from the spirit and scope of the novel concepts of thepresent invention.

I claim as my invention:

1. In a device for coating a traveling sheet, coating means on one sideof the sheet applying coating thereto, rotary doctor means on the sameside of the sheet behind said coating means in the travel of said sheetwiping excess coating from the sheet, and flexible shoe means on theopposite sidel of the sheet held against rotation and resiliently urgingsaid sheet against said doctor means throughout the full length thereofto control the extent to which excess coating is wiped from the sheet.

2. In a device for coating a traveling sheet, an applicator rollpartially submerged in a coating bath and rotating in the direction ofsheet travel to apply a coating to one side thereof, rotary doctor meanson the same side of the sheet behind said roll in the travel of saidsheet wiping excess coating from the sheet, and flexible shoe means onthe opposite side of the sheet held against rotation and resilientlyurging said sheet against said doctor means tov control the extent towhich excess coating is wiped from the sheet.

3. In a device for coating a traveling sheet, coating means on one sideof the sheet applying coating thereto, a doctor roll rotating oppositeto the direction of sheet travel and positioned on the same side of thesheet behind said coating means in the travel of said sheet wipingexcess coating from the sheet, and flexible shoe means on the oppositeside of the sheet resiliently urging said sheet against said doctor rollthroughout the full length thereof to control the extent to which excesscoating is wiped from the sheet.

4. In a device for coating a traveling sheet, coating means on one sideof the sheet applying coating thereto,

- rotary doctor means on the same side of the sheet behind said coatingmeans in the travel of said sheet wiping excess coating from the sheet,a flexible member delining with said doctor means a nip receiving thetraveling sheet, and diaphragm means resiliently urging said memberagainst the sheet throughout the full width thereof to control theextent to which excess coating is wiped ,from the sheet.

5. In a device for coating a traveling sheet, a tank maintaining a levelof liquid coating bath therein, an applicator roll mounted on the tankpartially submerged in the coating bath and rotating in the direction ofsheet travel to apply a coating to one side thereof, a doctor rollrotating oppositely to the direction of sheet travel and positioned onsaid tank on the same side of the sheet Vbehind said applicator roll inthe direction of travel of said sheet for contacting and for wipingexcess coating from the sheet, a ilexible shoe pivotally mounted on saidtank and defining with said doctor means a nip receiving the travelingsheet, and diaphragm means resiliently urging said shoe against thesheet throughout the full width thereof to control the extent to whichexcess coating is wiped from the sheet.

6. In a device for coating a traveling sheet, rst means on one side ofthe Sheet applying coating thereto, second rotary means on the same sideof the sheet behind said first means in the direction of travel of saidsheet rotatingly urged against said sheet to wipe excess coatingtherefrom, third flexible means defining with said second means a nipreceiving the coated sheet, and fourth means pneumatically loading saidthird means against said second means throughout the full width of thesheet to control the pressure at the nip and the amount of excesscoating wiped from said sheet by said second means.

References Cited in the file of this patent UNITED STATES PATENTS1,956,561 Coates May 1, 1934 1,956,562 Coates May l, 1934 1,987,183Dickhaut Jan. 8, 1935 2,206,170 Elam et al. July 2, 1940 2,672,119Ertner Mar. 16, 1954

